He and Mr. Charney came up with 10 traits of people who survived war, assault and disasters, as well as less traumatic events, and ultimately thrived. These people tend to be optimistic—thinking things will work out—and are able to accept what can’t be changed and focus on what can be, he says. They recognize that even though they didn’t have a choice in their loss, they are responsible for their own happiness.

Although genetics plays a role in being resilient, it isn’t a huge one. Resilience can be learned and enhanced, he says. For example, people can develop a more optimistic view by cultivating friendships with positive people and challenging negative thoughts.

“When you change the way you are viewing things, it has a pretty big impact on all sorts of things,” Mr. Southwick says. It isn’t easy to do, he acknowledges.

Harvard researcher Angela Duckworth defines grit as being "the ability to persist and passionately pursue your goal of winning, whatever it takes." According to Ducksworth, when it comes to success, grit is more important than talent. (99u)